For a passenger, calculating the cost per mile of airline travel is as simple as dividing the price of a ticket by the number of miles flown on a single trip. Air miles are calculated slightly different than land miles, however.
A land mile is 5,280 feet, and an air mile is 6,080 feet. Also, planes follow flight paths that may or may not be directly between two points, so it cannot be assumed that the land distance between two cities can simply be converted to air miles. Some airlines provide passengers with the amount of air miles for a flight when they book a trip as a part of frequent flyer programs. Since airlines need to be profitable in order to remain in operation, however, their formula for calculating the per-mile cost of airline travel is slightly different. When an airline calculates cost per mile of travel, it must consider factors such as the amount of fuel required for a trip, the salary of crew members as well as staff on the ground, and the cost of maintenance that is required as a result of how frequently the plane is in operation. The airline must then calculate how many seats it needs to fill in each flight in order to earn a profit.